Phase space analysis and cosmography of a two-fluid cosmological model

TL;DR

This paper analyzes a two-fluid cosmological model with a tachyon scalar field and modified chaplygin gas, using phase space and cosmography to study stability, late-time behavior, and comparison with the standard cosmological model.

Contribution

It introduces a phase space and cosmographic analysis of a novel two-fluid model combining tachyon and modified chaplygin gas, highlighting late-time acceleration conditions.

Findings

Late-time acceleration occurs only with tachyon fluid dominance.

Modified chaplygin gas does not support late-time acceleration.

The model exhibits a late-time scaling attractor with comparable energy densities.

Abstract

In the framework of spatially flat Friedmann-Lemaitre-Robertson-Walker (FLRW) space-time, we investigate a two-fluid cosmological model where a tachyon scalar field with self-interacting potential and a modified chaplygin gas with non-linear equation of state are taken as the background fluids. We perform phase space analysis of the autonomous system obtained from the cosmological governing equations by a suitable transformation of variables. Linear stability theory is employed to characterise the stability criteria for hyperbolic critical points. Numerical investigation is carried out for non-hyperbolic points. Our study reveals that modified chaplygin fluid dominated solutions cannot provide the late-time evolution. Late-time accelerated evolution is obtained only when the solution is dominated by tachyon fluid. This study also yields a late-time scaling attractor providing similar order of energy densities in its evolution. The adiabatic sound speed is evaluated for both the fluids and test the stability of the models independently. Further, we perform cosmographic analysis in the model independent way by evaluating all the cosmographic parameters and then $Om$ diagnostic is also found to compare our model with $\Lambda$CDM model.